* feat: add update document tags endpoint with observation invalidation
Adds PATCH /v1/default/banks/{bank_id}/documents/{document_id} to change
tags on a document without re-processing content.
- Updates tags on the document and all associated memory units atomically
- Invalidates observations derived from the document's memory units
- Resets consolidated_at on the document's own units for re-consolidation
- Also resets consolidated_at on co-source memories from other documents
that shared those observations (matching delete_document behavior)
- Triggers async consolidation when observations are invalidated
- 9 new tests covering all invalidation scenarios
UI: adds inline tag editor to the document detail panel in the control plane
Docs: new "Update Document Tags" section in documents.mdx with Python/JS examples
* refactor: simplify UpdateDocumentTagsResponse to {success: true}
* refactor: make PATCH /documents generic update_document endpoint
Renames update_document_tags → update_document (engine + HTTP + clients + UI).
Currently only tags are supported; the structure is open for future fields.
Tags are the only field with side effects (observation invalidation + re-consolidation).
